Power operated,predetermined torque release,bolt driver



C. FULOP May 6, 1969 POWER OPERATED, PREDETERMINED TORQUE RELEASE, BOLT DRIVER Filed Oct. 4, 1967 Fig.2

INVENTOR CHARLES FuLoP BY 94! i ATTORNEY United States Patent US. Cl. 192-56 2 Claims ABSTRACT OF THE DISCLOSURE A power driven tool for driving bolts or screws comprising a clutch-cone member forwardly movable on the tools spindle upon a predetermined resistance being offered to rotation. In this position the clutch-cone is in non-torque transmitting engagement.

This invention relates to bolt driving tools, and particularly to a power operated bolt driver having predetermined overload yielding means.

The primary object of this invention is to provide a power driven tool for driving bolts or screws, having clutching means for stopping the driving action at a predetermined torque, to prevent shearing and breaking of the screw or bolt being operated upon.

Another object is to provide a power driven tool of the type stated having means for positively adjusting the torque cut-off point between wide limits, by small discrete increments, as required by the particular conditions present. I

Another object is to provide a power actuated bolt driver that can be adjusted to draw up a series of bolts or screws to uniform tightness.

A further object is to provide a device of the type stated, that is reliable in operation, easy to adjust, of long life, and relatively inexpensive to manufacture.

These, and other objects of the invention, will become apparent from a reading of the following specification and claims, together with the accompanying drawing, wherein like parts are referred to and indicated by like referencenumerals, and wherein: 7

FIGURE 1 is a side elevation of the power operated, predetermined torque release, bolt driver, that is the subject of this invention, showing the device mounted on the drive shaft of an electric drill motor;

FIGURE 2 is a longitudinal sectional view of the device taken along the line and in the direction ofthe arrows 2-2 of FIGURE 1;

FIGURE 3 is a cross sectional view taken along the line and in the direction of arrows 33 of FIGURE 3;

FIGURE 4 is an exploded view of the device; and

FIGURE 5 is a perspective of the unmounted torque control'clutch cone. I,

Referring more particularly to the drawing, there is seen in FIGURE 1 the power operated, predetermined torque release, bolt driver, that is the subject of this in vention, broadly indicated by reference numeral 10, as it appears mounted on the drive shaft 12 of a hand held electric drill motor 11. It is, of course, to be understood that the unit could be driven by other means, such as a flexible shaft connected to a stationary motor.

Reference numeral 13 indicates a cylindrical body member and axial bore 14 abutting a substantially larger counterbore 16 through a shoulder 17. The body 13 is adapted to be mounted on the threaded end of the motor shaft 12 through mating threads 15 cut in its bore 14, as seen in FIGURE 2.

The forward end of the body 13 is externally threaded A cylindrical clutch ball cage 22 is fitted into the counterbore 16 and seated against the shoulder 17. The cage 22 is locked immovably in place by a set screw 26 which is mounted through a threaded hole 18 in the wall of the body member 13.

The cage 22 has an axial bore 24 with a frustoconical counterbore 25 in its forward half. Three, circumferentially spaced, radial bores 23 are out through the wall of the frustoconical bore 25, as is seen most clearly in FIG- URES 3 and 4.

A clutch ball 27 is seated in each bore 23, with its peripheral surface extending beyond the face of the wall of the cage conical bore 25. Each ball 27 is free to rotate in its containing bore 23.

Reference numeral 36 indicates a cap having an endclos-ure wall 37 and internal threads 39 adapted to engage the threaded neck 19 of the body 13, as seen in FIG- URE 2. The endwall 37 has a centered bore 38 through which a spindle 30 is journaled. The rear edge of the cap has a series of open-ended notches 42 cut therein which are sequentially engagable by a latch 20 slidably mounted on the body 13 and biased toward the notches by spring 21. A sleeve is fitted over the rear end of the cap, over the notches 42, and has locating lines engraved thereon, centered over each notch, for a purpose to be hereinafter disclosed.

The spindle 30 is square in cross-section, with a bearing collar 31 formed at the forward end of its square portion. The spindle 30 also has a threaded cylindrical section 32 forwardly of the collar 31, and another square section 33 which is adapted to engage the square, retaining seat, of a conventional socket wrench 43, as seen in FIGURE 1.

A clutch cone having an axial bore 46 of mating configuration, as seen in FIGURE 5, is slidably mounted on section 28 of spindle 30. The so-mounted clutch cone 45 is locked for rotation with the spindle 30, but free to reciprocate longitudinally thereof. A terminal head 29 is mounted, through a forced fit, on the extreme inner end of the spindle 30, as seen in FIGURE 4.

A coil spring 35, mounted on the spindle between the clutch cone 45 and the collar 31 acts to normally bias the cone away from the collar and against the head 29.

The spindle 30 is journaled through the cap bore 38, as seen in FIGURE 2, with the collar 31 against the inner side of the cap wall 37 and retained in place by a nut 34 mounted on the threaded portion 32 of the spindle, in spaced relation with the outer face of the wall 37. The nut 34 is drawn up until the spindle is just free to rotate in the journal bore 38, without binding. The nut is then locked in position, by peening.

The clutch cone 45 has a cylindrical portion 47 and a frustoconical portion 48, as is seen most clearly in FIG- URE 5.

The peripheral surface of the conical portion 48 is divided into three equally spaced tapered ca-m surfaces terminating in tapered radially extending teeth 49, adapted to be engaged by the clutch balls 27 when the clutch cone 45 is mounted within the clutch ball cage, as seen most clearly in FIGURE 3.

The cam teeth 49 are tapered from the base end of the conical section 48, where they are highest, to the apex of the cone, where they have zero height, as seen in FIG- URE 5.

When the device is assembled, as seen in FIGURE 2,

with the cap 36 fully drawn up, the clutch cone 45 interfits the cage bore 25 at its maximum penetration and the balls 27 engage the clutch cone cam teeth 49 at their greatest height, for maximum torque engagement.

In order to screw the cap 36 on to the body 13, the latch 20 is drawn back, to the left, so that it will not engage the 3 cap notches 42. After the cap has been rotated to the desired position the latch is released, and the spring 21 pushes it into the notch opposite, to hold the cap in place. This assures that the cap 36 will not change its position during operation of the driver 10, due to vibration or accidental movement by the operator.

The unit 10 is mounted on the drill motor shaft 12 by screwing the body 13, through its threads 15, on to the shaft 12, in which position the unit 10 will appear as illustrated in FIGURE 1, after a socket wrench 43 has been slipped on the spindle end 33.

Under "free-running conditions the body 13, cap 36 and spindle will rotate as a single unit with the motor shaft 12.

When the socket wrench 43 is engaged with the head of a bolt, or screw, not illustrated, and the motor 11 started, shaft 12 applies a rotating torque to the body member 13 which is transferred to the socket spindle 30 by thecage held balls 27 which engage the cam teeth 49 of theclutch cone 45, as seen in FIGURE 3. Since the clutch cone 45 is keyed to the spindle, its rotational torque is applied to the spindle 30 which in turn acts to rotate the bolt held in the socket wrench 43. The whole driver 10 now turns as a unit with the spindle 30 and the bolt being operated upon.

However, if the spindle 30 should be brought to a full stop by reason of the bolt engaged by the socket wrench 43 being frictionally held by reason of having been driven home, or having encountered resistance to penetration for any other reason, the body member 13 with its clutch cage 22 endeavors to continue rotating, and in doing so will apply torque forces to the clutch balls 27 which act to cause them to try to move longitudinally rearwardly, or to the left, as seen in FIGURE 2, of the clutch-cone cam teeth 49. Since the balls 27 are not free to move, but only to rotate, and since the clutch-cone 45 is free to move longitudinally of the spindle 30, the interplay of the developed forces causes the clutch-cone 45 to move forward on the spindle 30, away from the balls 27 and the spindle head 29, to compress the spring 35.

As the cone 45 moves the surface area of contact between the balls 27 and the inclined cam teeth 49 approaches zero. The torque at which such zero point of engagement is reached is determined by the compression of the spring 35, because in order to effect movement, the clutch-cone 45 must be moved against the spring 35.

When the zero point is reached the rotational torque being constantly applied to the body member 13 and cage 22 by the motor shaft 12 causes the balls 27 to ride over the cone, free of the cam teeth 49, on the cylindrical portion 47 thereof.

This disengages the body member 13 from the spindle 30, thus instantly relieving the torque being applied to the bolt, or screw, engaged in the socket wrench 43.

At the same time the compressed spring expands, to move the clutch-cone 45 along the spindle, back to its normal position against the spindle head 29.

When the clutch-cone 45 is returned to its normal position the balls 27 again roll into torque exerting engagement with the clutch-cone cam teeth 49.

If the resistance offered to rotation by the engaged bolt is still greater than the predetermined clutch-cone release torque, the releasing cycle is continuously repeated until the bolt driver 10 is disengaged from the bolt, or turned ofi.

Variation of the torque at which disengagement between the driving balls and the spindle cone cam teeth 49 occurs can be predetermined by moving the cap wall 37, on which the spindle 30 is journaled, toward or away from the body cage 22. This is effected by rotating the cap in either counterclockwise or clockwise directions, respectively, after first freeing the cap by disengaging the body latch 20 from the cap notches 42.

By referring again to FIGURE 2 it will be seen that as the spindle and its supported clutch-cone 45 is moved longitudinally of the axis of the body 13, toward the right, the point of engagement between the balls 27 held in the body 13 moves progressively nearer the apex of conical section 48 and its inclined cam teeth 49. Thus, the distance that will have to be travelled by cone 45, against the biasing. force of spring 35, before the zero point of contact between the balls and teeth is reached becomes less, and release will occur at progressively lower torques.

By having a guide line engraved on the cap sleeve 40 at each notch 42 and having an arrow 44 engraved on the latch 20, any desired torque release setting can be reestablished, at will, by engaging the latch in the proper notch.

The increment of increase or decrease in release torque, capable of being established and held by the device, is limited only by the width and spacing of the notches 42. Y i

If, instead of a socket wrench, a conventional chuck is mounted on the spindle end 33 the unit can be used to hold drill hits as well.

Due to the fact that the force of spring 35in returning the clutch-cone 45 against the spindle head 29 is directed away from the bolt, or screw, being held there is no hammering force directed against the bolt, or screw, which might deform their threads.

I claim:

1. An adjustable torque bolt driver, comprising in combination:

(a) a cylindrical body member, with its rear end adapted to be engaged by a motor driven shaft, having an axially centered frustoconical cavity therein with the base thereof open to the forward end of the body member; the wall of the frustoconical cavity having a plurality of clutch-ball seats spaced circumferentially thereof, intermediate its apex and base;

(b) a clutch-ball nested, for free rotation, in each of the seats with its peripheral surface extending beyond the cavity wall face;

(c) a hollow closure-cap threadedly engaged with the forward end of the body member, including, a forward end-wall having a bearing bore centered therethrough, said end-wall being moveable toward and away from the clutch-balls, upon rotation of the cap;

(d) a spindle journaled through the closure-cap endwall bearing bore, aligned with the axis of the body frustoconical cavity, the spindle having a socket wrench engaging portion at its outer end, beyond the cap end-wall, and a terminal head, at its extreme inner end, spaced from said cap end-wall;

(e) a clutch cone mounted on the spindle for positive rotation therewith, but free to reciprocate the length thereof between the spindle head and the cap endwall;

(f) the clutch cone having a frustoconical shape, complemental to that of the body cavity, with a cylindrical section at its apex, adapted to seat against the spindle head;

(g) the frustoconical section of the clutch-cone having adjacent, discontinuous, cam surfaces, one for each clutch-ball, abutting through axially inclined teeth extending between its base and apex and perpendicular to its axis of rotation;

the clutch-cone being normally biased against the spindle head, by an expansion spring mounted on the spindle between the cone and cap endwall, to a first position, wherein its cam teeth are in torque transmitting relation with the body clutch-balls at a predetermined maximum torque limiting location;

the clutch-cone being movable longitudinally of the spindle, against the expansion spring to compress same, when the transmitted torque exceeds the predetermined maximum limit, to a second position, whereat the clutch-balls are disengaged from the cam teeth and ride on the cylindrical section of the clutch-cone in nontorque transmitting engagement; said expansion spring acting to return the clutchcone to its first, torque transmitting, position upon cessation of the compressive force exerted thereagainst by the clutch-cone, when the cam teeth are disengaged by the clutch-balls; the torque at which the clutch-cone will be moved from its first to its second position being predetermined by rotation of the closure cap between adjusted positions. 2. An adjustable torque bolt driver, as in claim 1, wherein the closure cap has a series of spaced notches sequentially engageable by a latch mounted on the body 2/1960 Fulop 8152.4 XR 10/1960 Fulop 19256 XR CARLTON R. CROYLE, Primary Examiner.

10 ALLAN D. HERRMANN, Assistant Examiner.

U.S. Cl. X.R. 6429; 81-52.4 

